Security - Driveway Monitor Mod

Discussion in 'The Projects Forum' started by lokar, Aug 5, 2011.

  1. lokar

    Thread Starter New Member

    Aug 5, 2011
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    I have some driveway monitors like this, but the sending unit eats 9 volt batteries like crazy. Is there a way to mod the motion sensor/sending unit to use a more economical power supply? A big 6 volt battery, a little solar panel for a rechargeable batt of some sort, whatever.... I foresee mounting the sensor in a larger box of some sort, housed somehow with a larger, longer lasting battery setup than the one 9-volt that it uses now. Actually, as bad as the expense is having to change it out so often. I'm handy enough to do the work, just not knowledgeable enough to figure out what needs to be done!

    The receiver part of the monitor setup can be plugged into the house power, eliminating the need for batteries in the receiver/alarm.

    I'd like to make several of these setups to be able to sprinkle around my residence.

    Thanks for any ideas and assistance.....

    Z
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    Does it tend to generate false alarms?

    hgmjr
     
  3. #12

    Expert

    Nov 30, 2010
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    Might I suggest a solar cell and rechargable battery? 9V batteries are notoriously feeble. A solar cell might be able to keep up with the demand.

    Nimh batteries are the wave of the future, but they're picky about charging. A Ni-cad 9V would work better.
     
  4. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I had a very similar wireless monitor that I setup to alarm when the mail had arrived. It was located inside a mailbox and should not have generated any alarms, but once a day.
    It also sucked up 9V batteries like crazy. Don't know what the standby current is on these things, buy a 9V battery only lasted 10 days or so. Not a good device, not really something I even wanted to power with a wall adapter.
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I might even try to steer you away from the single 9V battery altogether to a 6pk of AA NiCad's with a solar cell. You would have to regulate the voltage to around 8.4V or 8.6V depending on the current capabilities of the panel.
     
  6. wayneh

    Expert

    Sep 9, 2010
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    What a dumb design! An IR device like this needs a fair amount of current and the designer had to know a 9V battery wouldn't last long. How secure is a system that goes dead?

    Anyway, I agree that solar is a good choice for recharging in this application, assuming your transmitters are near a sunny spot. The trouble is that the cheapest panels - the ones you could scavenge from solar landscape lights - are for 1.2v nicads. You could use several in series plus a blocking diode, but that requires building something and may wouldn't be very elegant. A pain for more than one, too. Lots of larger panels are for charging 12v batteries, but I can't say I've seen panels meant for the (puny) 9V rechargeables. Maybe a 12v panel with a current limiting resistor or even a regulator to burn off the excess voltage and protect the battery. Thing is, you don't need much current but you do need voltage.
     
  7. lokar

    Thread Starter New Member

    Aug 5, 2011
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    I suppose I have to either research or test the unit to find out how fast it drains the power source, to make sure it's possible/practical to put a solar cell on it that's efficient enough to keep whatever battery pack is used charged up?

    The solar aspect is interesting, but since it needs the sun and is therefore limited use, I probably will opt for whatever battery pack/110v recharging setup seems the most practical and long-lasting at the same time, and make backup battery packs to have charged and ready for swap-out. Actually I'd make both if we (read: you guys) figure it out.

    Thanks for the ideas so far....

    z
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
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    I'd probably just use a 12V sealed lead acid battery (SLA) after taking a look at the circuit components to make sure they can handle a few more volts.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Or a 4-pack of rechargeable AAs if the thing works at the lower voltage. Since the 9V fades away quickly, I'm guessing the device would work fine down to 4v or so. The rechargeable AAs are the most economical and convenient form these days.
     
  10. iONic

    AAC Fanatic!

    Nov 16, 2007
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    I don't know how many detectors you have or their perceived intention/need for their use, , but I might consider a few pieces of electrical PVC with a 9V switching supply side. Your worries will be over. You could still do the same with a single solar panel and a 12V battery with the same electrical PVC underground.
     
  11. #12

    Expert

    Nov 30, 2010
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    I'm calculating about 2ma average draw. I think ANY solar panel could do that.
     
  12. lokar

    Thread Starter New Member

    Aug 5, 2011
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    Several opinions and ideas, thanks for the interest.... as far as the use for these things, I like the idea of the sending unit being able to "take care of itself" for a while instead of needing a battery change every week... that makes it more mobile, so I can set one to cover the plants the deer keep eating, and one looking across my back porch... you could set it so you'd know if a kid or pet was on the move... lots of stuff.

    z
     
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